Overbooking is intentional policy. It has nothing to do with data consistency.
To the contrary, consistency is extremely important so that they overbook by exactly the right amount, to compensate for the statistically expected no-shows.
It is a form of coherence for the system, though. And in the spirit of the same ideas. That is, it is an intentional policy for databases, too.
And there is no "exactly right amount" that makes it work. They keep options for forcing people off flights if they planned it wrong.
Is also why they don't let gate agents over sell a flight. They keep a stronger consistency on that, for this exact reason. Over selling would fit in what someone else called external consistency.
To the contrary, consistency is extremely important so that they overbook by exactly the right amount, to compensate for the statistically expected no-shows.